Fixes for mod_av related to signalwire/freeswitch#2202

[Korynkai]

This is refactored from the patch listed in #2202 to guard against the exact library versions these changes occurred at.
The changes are as follows:

• AVOutputFormat::priv_data_size is marked private and no longer exists in the public API as of FFMPEG 6.0, but found hidden in AVOutputFormat as part of FFOutputFormat.
• AVCodecContext::ticks_per_frame was deprecated as of FFMPEG 6.1.
• libavcodec notes 'do not use avcodec_close()' as of FFMPEG 3.1, use avcodec_free_context() instead.
• AVFrame::key_frame was deprecated as of FFMPEG 6.1, use AVFrame::flags instead.
• AVInputFormat::read_seek and AVInputFormat::read_seek2 no longer exists as of FFMPEG 7.0. This seems to only be used for logging purposes, so guard this functionality accordingly.

[arduent]

This seems to work for me with FFMpeg 7, but also need a few other changes i think.. (but also make sure it works with old versions of FFMpeg too, i suppose...

# ffmpeg -version
ffmpeg version N-119396-g48c0dba23b Copyright (c) 2000-2025 the FFmpeg developers
built with gcc 12 (Debian 12.2.0-14)
libavutil      60.  2.100 / 60.  2.100
libavcodec     62.  1.102 / 62.  1.102
libavformat    62.  0.102 / 62.  0.102
libavdevice    62.  0.100 / 62.  0.100
libavfilter    11.  0.100 / 11.  0.100
libswscale      9.  0.100 /  9.  0.100
libswresample   6.  0.100 /  6.  0.100
libpostproc    59.  1.100 / 59.  1.100

add_stream() around line 525 in src/mod/applications/mod_av/avformat.c

add_stream(arg,arg,arg,arg,,,,) {

const enum AVSampleFormat *sample_fmts;
int ret;

...etc...
c = av_get_codec_context(mst);

ret = avcodec_get_supported_config(c, *codec, AV_CODEC_CONFIG_SAMPLE_FORMAT,
                                                0, (const void **) &sample_fmts, NULL);
if (ret<0) {
	return status; //no sample formats!
}

/* i suppose we want sample_fmts[0] but maybe this 
    needs re-worked.. ie not return if ret<0... in this case 
    c->sample_fmt will never be set to AV_SAMPLE_FMT_FLTP
*/
switch ((*codec)->type) {
		case AVMEDIA_TYPE_AUDIO:
			c->sample_fmt  = sample_fmts ? sample_fmts[0] : AV_SAMPLE_FMT_FLTP;
			c->bit_rate    = 128000;
			
			...

also need to change some constants in avcodec.c:

src/mod/applications/mod_av/avcodec.c

FF_PROFILE_H264_BASELINE becomes AV_PROFILE_H264_BASELINE
FF_PROFILE_H264_MAIN becomes AV_PROFILE_H264_MAIN
FF_PROFILE_H264_HIGH becomes AV_PROFILE_H264_HIGH